Current hospital and clinical laboratories are furnished with highly sophisticated and automated systems which have capabilities to run up to several thousand samples per day. These high throughput systems have automatic robotic arms, pumps, tubes, reservoirs, and conveying belts to sequentially move tubes to proper position, deliver the reagents from reservoirs, perform mixing, pump out the solutions to waste bottles, and transport the tubes on a conveyer to various modules.
Such complicated and high costs systems are generally not desired, and may not be readily adapted for short-run or individual testing procedures.
Immunoassays are important analytical systems used today in clinical laboratories. Existing Point-of-Care (POC) immunoassay devices utilize a wide variety of techniques for sample analysis. The drive towards immunoassay POC technology has produced several rapid immunoassay devices that yield results at a doctor's office or clinic within minutes. Examples of conventional POC immunoassay devices include relatively simplistic designs such as dip-sticks and test strips using relatively inexpensive support mediums that are easily operated by health practitioners as well as lay people.
In order to deliver a consistent sample volume to a reaction chamber or region of an immunoassay device, conventional designs have employed various principles for controlling the dynamic fluid movements, which may rely on several principles utilized either individually or in combination. These include controlled fluid movements in channels and capillaries which typically need to be designed for the specific fluid. It may be unsuitably complex to manufacture systems with such channels and capillaries to within specific tolerances, typically at the micron or submillimeter order of magnitude. For example, in such systems, liquids are transported by means of capillary forces which in turn makes high demands on the accuracy and form of the capillary channels and consequently results in correspondingly expensive and complex manufacturing processes. Additional fluid properties may also need to be specifically addressed in such systems, such as viscosity, etc.
Complex mechanisms which generate external forces have also been employed in some conventional testing devices to deliver consistently measured volumes to the reaction chambers in order to facilitate fluid migration and movements. There are conventional devices that have employed vacuum, centrifugal forces, positive pressure or relying on internal fluid forces. These forces include pressure in a negative (vacuum) or in a positive form. Also, mechanisms for generating centrifugal forces have been employed to control fluid volumes, as well as the use of electroosmotic forces.
Such systems may be relatively complex, which may not be suitable for many POC applications. For example, liquid transport by externally applied forces such as by centrifugation, rotation or by pumping generally require additional costly apparatuses such as centrifuges or pumps. In addition, these systems may often require additional process steps which usually have to be carried out outside of the device because such microfluidic devices can often only be equipped with dry chemistry reagents for manufacturing and stability reasons.